In this paper, we describe the progress of four male, legally-detained personality disordered offenders in a group treatment programme for angry aggression. “Controlling angry aggression” is a 15-session, structured, cognitive-behavioural programme that is part of a wider integrated, multidisciplinary treatment programme run within a specialist personality disorder treatment unit. Psychometric tests showed that three of the four patients improved over the course of the treatment programme. Behaviour ratings of staff and patients concurred, allowing confidence in patients' self-report of anger. No change in behaviour was evident over time for any patient, but initial low rates of aggression allowed little room for improvement. Self-monitored anger and aggression scores did vary markedly over time, and since behaviour remains stable despite anger, this indicates that these patients can control their behaviour. One patient did not improve, and reasons for this are examined, concluding with a reminder of the need for rigorous selection of patients for treatment programmes.